The current in a bayou near lafayette, louisiana, is 4 miles per hour. A paddle boat travels 48 miles upstream in the same amount of time it tkaes to travel 72 miles downstream. Find the speed of the boat in still water? how do you set this problem up ?

Question

anonymous · Answer

72=4t+rt
48=rt-4t

anonymous · Answer

How do i even begin to solve this problem?

anonymous · Answer

solve for t. substitute into other equation

anonymous · Answer

48=t(r-4)

anonymous · Answer

I'm so confused to be honest. :(

anonymous · Answer

so solve for t.  48/(r-4)=t

anonymous · Answer

plug it into the other equation

anonymous · Answer

72=t(4+r)

anonymous · Answer

t = d/r
Let r be the speed of the boat in still water.  The elapsed time for both trips is the same.  The LHS is the expression for the upstream trip.  Solve the following for r:$$\frac{48}{r-4}= \frac{72}{r+4}$$r = 20 mph